Multi-digit display apparatus

ABSTRACT

A multi-digit display comprises an electrode board having a plurality of display sections and a transparent plate which is transparent at least for portions facing the individual display sections, the transparent plate and electrode board being stacked, the stack being hermetically sealed around the periphery thereof, the electrode board carrying cathodes arranged in groups for the individual display sections and anodes formed in portions surrounded by the individual cathodes and in portions surrounding the individual cathodes.

' United States Patent Kouyama et al. 1 Oct. 14, 1975 [54] MULTI-DIGIT DISPLAY APPARATUS 3,675,065 7/1972 Wame 313/1095 3,684,909 8/1972 Caras 313/54 [751 Inventors: Masahar Kouyama; Klsuo 3,756,693 9 1973 Ota 313/1095 Nakada, both of Mobara; Toyokazu Odaka, Ichimiya; Akio Miyamoto, Mobara, of Japan Primary ExaminerAlfred L. Brody [73] Assigneez Hitachi Tokyo Japan Assistant ExaminerDarwin R. Hostetter Attorney, Agent, or FirmCharles E. Pfund, Esq. [22] Filed: Aug. 2, 1973 [21] App]. No.: 384,887

[57] ABSI'RACT [30] Foreign Application Priority Data Aug. 4, 1972 Japan 47-77701 A multi-digit display comprises an electrode board Aug. 4, 1972 Japan... 47-77703 having a plurality of display sections and a transparent Aug. 4, 1972 Japan 47-77706 plate which is transparent at least for portions facing the individual display sections, the transparent plate [52] US. Cl 313/519; 313/517 and electrode board being stacked, the stack being [51] Int. Cl. HOlj 7/42 hermetically sealed around the periphery thereof, the [58] Field of Search 313/54, 109.5, 513, 514, electrode board carrying cathodes arranged in groups 313/517, 520, 521, 519 for the individual display sections and anodes formed in portions surrounded by the individual cathodes and [56] References Cited in portions surrounding the individual cathodes.

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US. Patent Oct. 14, 1975 Sheet3 of? 3,912,964

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MULTl-DIGIT DISPLAY APPARATUS BACKGROUND OF THE INVENTION This invention relates to multi-digit display apparatus and, more particularly, to multi-digit display apparatus for displaying a plurality of patterns such as figures and symbols arranged in a row by means of glow discharge in gases.

The usual multi-digit display apparatus utilizing glow discharge in gases has a plurality of parallel display sections each consisting of display cathodes arranged such as to be able to represent desired patterns and a common anode, these sections being sealed within the same envelope. In this system, a voltage is applied selectively to the cathodes with respect to the anode for displaying a desired pattern, and voltage application is controlled on a time division basis for the individual digits. The usual flat multi-digit display apparatus comprises a cathode board having an arrangement of a plurality of parallel groups of elementary display cathodes, the cathodes in each group being arranged such as to constitute a display section, anodes individually facing the respective display sections, a transparent plate of glass or like material and a spacer intervening between said cathode board and anodes and defining discharge spaces. These elements are stacked, and the stack is hermetically sealed around its periphery by means of crystalline frit glass or non-crystalline sealing glass. The package or envelope thus formed is evacuated and is then filled with such discharge medium as neon or argon gas to complete the flat multi-digit display apparatus.

With the flat multi-digit display appratus of such construction, however, cathode and anode are arranged to oppose each other through a discharge space. Therefore, the display apparatus cannot be made very thin due to limitations imposed by the electrode structure. Also, since the cathode and anode oppose through a discharge space, the display pattern must be observed through the anode electrode, and it is necessary to employ a mesh-like anode or transparent anode. In case of using a mesh-like anode, however, the clearness of the display is sacrified, and also the number of parts is extremely increased. In case of using a transparent anode, for instance one made of NESA (a tradename) film, the transparent electrode is subject to damage due to heat at the time of sealing.

To solve the above problems, there has been proposed an arrangement comprising an electrode board having a plurality of display sections and a transparent plate which is transparent at least for portions facing the display sections, said electrode board and transparent plate being stacked such as to define discharge spaces and hermetically sealed around their periphery, the electrode plate being provided with cathodes arranged in groups capable of representing desired patterns and anodes formed in portions surrounded by the cathodes, the cathodes and anodes being formed in the same plane, for instance as disclosed in U.S. Pat. No. 3,231,776 and in U.S. Pat. No. 3,327,154.

However, where the anodes are formed only in portions surrounded by the cathodes which are arranged to represent an Arabic fure eight, a decimal point display is prone to instable discharge, resulting in irregular glow. Also, with the flat multi-digit display apparatus of the above construction the surface area of the anode is limited by the area of the portion enclosed by the cathode, so that it is impossible to increase the anode surface area beyond the limit. Therefore, the anode area is smaller than the total cathode area, so that the firing voltage is inevitably high. Also, the current density ad- 5 jacent the anode surface is high, giving rise to the glow near the anode or so-called anode glow column, thus adversely affecting the desired pattern display.

Also, the flat multi-digit display apparatus of the disclosed construction uses a white window plate, with its inner surface scattering the light of cathode glow, so that the display pattern is very unclear.

Further, in the flat multi-digit display apparatus of the disclosed construction the initiation of the discharge depends upon initial electrons produced due to cosmic rays and external light, so that delay time is involed from the instant of application of driving voltage till the initiation of the discharge, the delay time being extremely long in a dark room where external light is shut off.

Furthermore, the multi-digit display apparatus of this construction uses a crystalline glass chiefly composed of lead for hermetically sealing the periphery of the stack. Therefore, unless the sealing is done in a weak oxidizing atmosphere such as in air, the crystalline glass is rendered black or gray due to reduction of the lead oxide, or bubbles are formed in the glass so that the glass is rendered into a sponge-like form. In such case, the hermetical seal cannot be obtained. Usually, the portion of the display electrodes of the aforementioned multi-digit display elements is constituted by metal. Therefore, if the crystalline glass is subjected to sealing operation in air, the display electrodes are oxidized since the crystalline glass usually requires a sealing temperature of 400C or above, so that there would result irregular glow of the discharge in the display section or increase of the firing voltage and in extreme cases failure of the glow discharge.

SUMMARY OF THE INVENTION Accordingly, an object of the invention is to provide a multi-digit display apparatus having a very small thickness dimension.

Another object of the invention is to provide a multidigit display apparatus without using any mesh anode in front of the display pattern and capable of providing clear display.

A further object of the invention is to provide a mu]- ti-digit display apparatus consisting of a very small number of parts.

A further object of the invention is to provide a multi-digit display apparatus having increased anode area and improved discharge characteristics.

A further object of the invention is to provide a multi-digit display apparatus, in which the scattering of light by the window plate is prevented to provide for clearer pattern display.

A further object of the invention is to provide a multi-digit display apparatus, in which the discharge can be very readily initiated.

A further object of the invention is to provide a multi-digit display apparatus, with which the oxidation of electrodes at the time of sealing is prevented to provide for improved discharge characteristics.

To achieve the above objects, the multi-digit display apparatus according to the invention comprises an electrode board having a plurality of display sections and a transparent plate which is transparent at least for portions facing the individual display sections, said transparent plate and electrode board being stacked, the stack being hermetically sealed around the periphery thereof, said electrode board carrying cathodes arranged in groups for the individual display sections and anodes formed in portions surrounded by the individual cathodes and in portions surrounding the individual cathodes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded perspective view of one embodiment of the multi-digit display apparatus according to the invention.

FIGS. 2a to 211 illustrate an example of the method of manufacturing the multi-digit display apparatus shown in FIG. 1.

FIG. 3 is an enlarged scale view showing one display section (one digit) of the multi-digit display apparatus produced in the method of FIG. 2.

FIG. 4 is a sectional view taken along line IVIV in FIG. 3.

FIG. 5 is a view similar to FIG. 3 but showing one display section of another embodiment of the multi-digit display apparatus according to the invention.

FIG. 6 is a sectional view taken along line VIVI in FIG. 5.

FIG. 7 is an exploded perspective view showing a further embodiment of the multi-digit display apparatus according to the invention.

FIG. 8 is an enlarged scale fragmentary sectional view showing a still further embodiment of the multidigit display apparatus according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a fragmentary exploded perspective view of one embodiment of the multi-digit display apparatus according to the invention. It is constructed to display l3-digit figures. In the Figure, reference numeral 1 designates a rectangular transparent plate of glass or like material, and numeral 2 a window plate having seethough windows for individual digits. The window plate is coated in black color and has low light reflection coefficient. Numeral 3 designates an electrode board having an electrode structure consisting of display cathodes 4 arranged in groups each in the form of an Arabic figure eight, anodes 5 and 6 arranged in portions surrounded by the display cathodes 4 and portions surrounding them, electrodes 7 representing decimal points, terminals 8 for selectively energizing these electrodes and electric wiring connecting the electrodes and terminals and printed in multi-layer printing. The transparent plate 1, window plate 2 and electrode board 3 of the above structures are stacked one over another, and the periphery of the stack is hermetically sealed with a binder such as low-melting glass, organic adhesive or special binders. The sealed envelope is evacuated and then filled with an inert gas such as mixture of neon and argon and, if necessary, mercury vapor, thus completing a multi-digit display unit.

With the multi-digit display apparatus of this construction, by applying voltage between terminals 8 leading to selected display cathodes 4 and terminals leading to selected anodes 5 and 6 glow discharge is produced between the selected display cathodes 4 and anodes 5 and 6 for the display of desired glow patterns. The like display cathodes 4 for the individual digits are connected to the same terminal 8, so that the display of desired patterns (figures) may be obtained by selectively supplying voltage to the terminals 8 leading to the respective anodes 5 and 6 for the individual digits on a time division basis. Also, the multi-digit display apparatus of this construction consists of only three plate members, namely transparent plate 1, window plate 2 and electrode board 3, so that it requires a very small number of parts compared to the prior-art apparatus of this kind, has small thickness dimension and is suited for mass production. Further, since the individual electrodes and wiring leads are arranged on a single electrode board, the handling and assembling are very easy, and the electrodes and wiring leads can be simply formed by multi-layer printing. Since the cathodes 4 and anodes 5 and 6 are formed substantially in the same plane, the solid angle of glow is very large, with light emanating from the cathode falling upon the inner side of the window plate 2. However, since the window plate is coated in a color of low light reflection coefficient as mentioned earlier, the reflection of light by the inner side of the window plate 2 is prevented, so that very clear display patterns can be obtained.

The method of manufacture of the multi-digit display apparatus of the above construction will now be described step by step with reference to FIGS. 2a to 2h.

A ceramic powder material chiefly composed of aluminum oxide of percent of higher purity is kneaded together with a binder and a solvent into a paste, which is formed into a sheet form about 2 mm thick and is then dried to prepare a dielectric sheet of a strip-like form as shown in FIG. 2a. The dielectric sheet is then formed with positioning holes 10 in its opposite edge portions to complete the plate 11. Then, busbars 13a to 13/1 extending in the longitudinal direction of the plate 11 for connection to cathodes, leads 14a to 14/1 for connection to anodes, a lead 15 for connection to cathodes, leads 16a to 1611 for connection to cathodes and anode terminals 17a to 1711 are formed by using a conducting material with the screen printing technique. As the conducting material may be used a conducting paste composed of conductive high-melting powder of tungsten, molybdenum, manganese, titanium and platinum or oxides of these materials kneaded together with a binder and a solvent. The substrate 11 formed with the afore-mentioned printed pattern of the conducting material is dried by holding it in air at a temperature of about C for about 15 minutes, whereby the conductor layer is firmly bonded to the substrate 11.

Then, a first dielectric layer 18 is printed on the substrate 11 of FIG. 2b, as shown in FIG. 2c. At this time, the first dielectric layer 18 is formed by screen printing such as to leave cathode connection points 19 on busbars 13a to 13h for connection to the cathodes, anode connection points 20 positioned at opposite ends of the leads 14a to 14h for connection to anodes, the connection points 16a to. 16h positioned at the end of the cathode take-out lead 15, and connection points 21 positioned adjacent the inner ends of the anode terminals 17a to 1711. These connection points have a diametrical dimension of, for instance, 0.3 to 0.1 mm, and they can be formed very easily by using the screen printing technique. The first dielectric layer 18 may have a thickness of about 40 microns to 0.5 millimeter and very small compared to the diameter of the connection points. For this first dielectric layer 18 the same material as for the substrate 11 may be used. In this case, however, some improvements are required in view of obtaining a viscosity suited to the printing and also in view of the problem of pin hole. For example, a mixture consisting of 50 percent by weight of ceramic powder chiefly composed of aluminum oxide, 20 percent by weight of polyvinyl butyl alcohol or ethyl cellulose as binder having adhesive character suited to the printing, and 30 percent by weight of butyl carbitol acetate as solvent for maintaining the viscosity may be used.

The substrate 11 printed with the first dielectric layer 18 is subjected to a drying treatment in the same way as has been mentioned earlier. Thereafter, cathode take-out leads 24 extending between the figure eight shape cathodes 22 except for cathode connection points 19 but connected thereto and connection points 23 positioned on the busbars 13a to 13h for connection of the individual connection points 16a to 1611 and common cathodes are formed using a conducting material similar to one mentioned above and with the screen printing technique. In this printing, the conducting material printed on the first dielectric material 18 readily flows in the connection points since the first dielectric layer 18 is very thin compared to the diameter of the connection points, so that it can be readily and reliably connected to the conducting layer underlying the first dielectric layer 18. Thus, in the state shown in FIG. 2d the individual common cathodes 22 are electrically connected through the cathode connection points 19 to the busbars 13a to 1311, while the busbars 13a to 13h are connected through connection points 23, leads 24, connection points 16a to 1611 and leads to the respective cathode terminals 12a to 1211. If the cathodes 22 are printed to overlie the connection points 19, the surface of the cathodes are prone to irregularities giving rise to irregular glow. Because of this ground, the connection points 19 have to be provided such that they will not overlap the cathodes 22.

A second dielectric layer 23 is then printed such as to leave the anodes 22 and the connection points 20 positioned at opposite ends of the leads 14a to 14h for connection to anodes in the manner as mentioned earlier, as shown in FIG. 2e.

Then, the first anodes 24 surrounded by the cathodes 22, the second anodes surrounding the cathodes 22 and connected to the connection points 20 and leads 26 connected between the second anodes 25 and connection points 21 of the anode terminals 17a to 1711 are printed on the second dielectric layer 23 by using a conducting material similar to one mentioned earlier, as shown in FIG. 2f. The conducting layer thus printed is dried in the same way as mentioned earlier. The first and second anodes 24 and 25 are commonly connected through the connection points 20 and leads 14a and 14b to constitute a single anode for each digit. The anodes of the individual digits are connected through the leads 26 and connection points 21 to the respective anode terminals 17a to 17m.

A third dielectric layer 27 is then formed by the screen printing such as to leave the cathodes 22, first and second anodes 24 and 25 and decimal point electrodes by using a dielectric material similar to one mentioned earlier, as shown in FIG. 2g. If the dielectric material of the third dielectric layer 27 is white, the display surface will scatter light of the cathode glow, thus adversely affecting the clearness of the glow display. In order to overcome this problem, the material of the third dielectric layer 27 may be colored to a color of reduced light reflection coefficient. For example, the material may be colored to gray or black color by adding titanium oxide to the ceramic powder material chiefly composed of aluminum oxide. Alternatively, by adding cobalt oxide violet color may be obtained, and by adding manganese dioxide pink or brown color may be obtained.

The substrate 11 carrying the multi-layer print structure as shown in FIG. 2g is then trimmed to obtain the electrode board 28 as shown in FIG. 2h. The electrode board 28 thus obtained is held in an non-oxidizing atmosphere at a temperature of l,400to l,650C for about 1 hour for simultaneously baking the substrate 11 chiefly composed of aluminum and dielectric layers and conducting layers formed by printing. During the baking step, such additives as binder scatter away or are baked, so that the size of the electrode board 28 is reduced by about 15 percent. This extent of size reduction should be borne in mind in preparing the substrate to obtain an electrode board having precise dimensions and shape.

The transparent plate and window plate mentioned earlier are stacked over this electrode board 28, and the periphery of the stack is hermetically sealed. Then, the resultant envelope is evacuated and then the discharge medium is introduced into its interior to complete the multi-digit display apparatus.

FIG. 3 shows an enlarged scale view of a portion of the electrode board 28 manufactured through the afore-mentioned steps of FIGS. 2a to 2h only for one digit, and FIG. 4 is a sectional view taken along line IV-IV in FIG. 3. In these Figures, like reference symbols as in FIG. 2 are used. As is shown, the first conductor layer consists of the anode terminals 17a to 17:1 for connection to the external circuitry, cathode terminals 12a to 1211 also for connection to the external circuitry, busbars 13a to 1311 for connection of the like cathodes, leads 14a and 14b for commonly connecting the divided anodes and cathodes take-out leads 15. The first dielectric layer 18 is printed over the first conductor layer except for predetermined connection points. Printed over the first dielectric layer 18 is the second conductor layer consisting of figure-eight-shaped cathodes 22a to 22g and leads connected at one end to the cathodes 22a to 22h and at the other end to busbars 13a to 1311 of the first conductor layer through the connection points of the layer 18. If the cathodes 22 are directly connected to points provided directly under them for connection to the first conductor layer, irregularities would be produced in the surface of the cathodes 22. Since in the gas discharge display it is the cathodes that provide glow, even slight irregularities of the cathode surface result in irregular glow. Formed over the second conductor layer except for the cathode 22 and predetermined connection points is the second dielectric layer 23. It serves to cover the cathode connection points and let them be substantially in the same plane as and near the cathode. If it is intended to provide the anodes without using the second dielectric layer 23, it is necessary either to have the cathode and anode sufficiently spaced apart or to provide the anodes directly in the first conductor layer. In the former case, the structural freedom is lost, so that the electric characteristics are greatly afiected. In the latter case, the discharge is prevented. Provided over the second dielectric layer 23 is the third conductor layer consisting of the anodes 24 and 25 and leads 26 connecting the anodes to the respective anode terminals 17a to 17h and leads 14a and 14b for mutually connecting the anodes. Printed over the third conductor layer except for the cathodes and anodes is the third dielectric layer 27. For successively printing the conductor layers and dielectric layers over a single dielectric substrate for providing the anodes and cathodes for displaying de sired patterns such as figures and characters and leads for leading these electrodes to the external circuitry, multi-layer printing is required. More complicated electrode board structures may be fonned by increasing the number of printed layers, and at least three conductor layers and three dielectric layers are necessary in order to form the two kinds of electrodes efficiently and without giving rise to sacrifice in the display effect. If it is intended to arrange the anodes on the first dielectric layer and the cathodes on the second dielectric layer, the structural freedom of either anodes or cathodes is lost. Thus, by arranging the cathodes on the first dielectric layer and the anodes on the second dielectric layer maximum effects can be obtained with a minimum number of steps. The electrode board obtained in this way can be directly used as a component part of the display apparatus.

As has been mentioned, by providing the anodes 24 and 25, the former in portions surrounded by the cathodes 22a to 22g and the latter in portions surrounding the cathodes 22a to 22g, the cathodes and anodes can be spaced apart substantially by a constant distance, so that it is possible to uniform glow over the individual portions of the cathode to obtain obtain clear display patterns.

FIGS. and 6 show another embodiment of the multi-digit display apparatus according to the invention. In the Figures, like parts to those in FIGS. 3 and 4 are designated by like reference symbols. In this embodiment, the surface area of the outer anode 25 surrounding the cathodes is increased compared to that of the previous embodiment of FIGS. 3 and 4.

By setting the total area of the anodes 24 and 25 to be broader than the total area of the cathodes 22a to 22g in this way, the firing potential can be reduced by several volts. Of course, this time the dielectric layer covering can be dispensed with.

The advantage of having the anode area greater than the cathode area will now be discussed in more detail. In case of sealing the periphery of the stack of upper plate, intermediate plate and electrode board with such sealing means as frit glass as according to the invention, unless the sealing is done in an atmosphere of weak oxidizing character such as air at a temperature of about 400C to 500C, reduction of lead oxide reduces since the crystalline frit glass usually consists of lead glass as main component, leading to blackening of the sealing portion and formation of bubbles, so that hermetical seal in vacuum cannot be obtained. From this ground, the sealing is usually carried out in air. Under the aforementioned treatment conditions, however, the anodes and cathodes on the electrode board would be oxidized. Provided the oxidation of the cathodes is slight, clear cathode metal surface may be obtained by subjecting the oxidized surface to a spattering or so-called aging treatment after evacuation of the envelope and filling it with the discharge medium. However, applying this also to the anodes is difficult since the anode usually has a greater area per segment than the cathode area. Also, in case of conducting the aging of the anodes, the spattered metal is likely to attach to the insulating portion between cathode and anode, resulting in insulation failure. Therefore, this process is not employed in practice, and the anodes are left oxidized. With such anode having the oxidized surface, the effective surface area as the discharge tube electrode is thought to be considerably smaller than the actual anode area; empirically, only a fraction of the total area is thought to be effective. Since the interelectrode gap d between cathode and anode and sealed gas pressure P are selected such that the firing voltage Ez, which is the fundamental characteristic of the discharge tube and is detemiined by the product of the gap d and pressure P and the surface state of the electrode, is normally minimum, with the oxidized anode surface the firing voltage is slightly increased. 4

While in the preceding embodiments use has been made of a non-baked substrate chiefly composed of aluminum oxide, it is by no way intended to be limitative, but non-baked substrates, for instance consisting of fosterite powder or glass powder, may be used as well.

FIG. 7 shows a further embodiment of the multi-digit display apparatus according to the invention. In the Figure, like parts to those in FIG. 1 are designated by like reference symbols. This embodiment is different from the embodiment of FIG. 1 in that a radioactive material consisting of radioactive isotopes emitting only B-rays such as Ni, Pm and H or a compound composed thereof is provided to the inner walls of seethrough windows 30 for the individual display sections in the window plate 2. The radioactive material 31 may be provided to the inner wall of the windows 30, for instance, by inserting a brush dipped in the ratioactive material in the window 30 with a number of plates same as the window plate 2 stacked together or immersing the window plate 2 in the radioactive material.

With the multi-digit display apparatus of this construction, by applying a voltage between selected cathode terminals 8 and selected anode terminals 8 discharge is produced between selected cathodes 4 and anodes 5 and 6 to obtain a desired glow pattern. Since the afore-mentioned radioactive material 31 is coated over the side wall of the windows 30 of the window plate 2, the discharge can be initiated with radioactive rays emitted from the radioactive .material 31 or initial electrons produced by the radioactive radiation. Thus, the initiation of the discharge need not depend upon the external light, and the discharge may be initiated readily even in the dark room. Also, the discharge delay is extremely reduced compared to the prior-art apparatus. While it may be effective to apply the radioactive material 31 in various positions, best effects may be obtained by applying it over the inner wall of the window plate 2. By applying the radioactive material 31 over the inner wall of the window plate 2 it is possible to have largesolid angle and large fly distance, so that ,B-rays emitted from the radioactive material 31 can excite the discharge space substantially uniformly. It is desirable from the standpoint of safety to select a radioactive material emitting weak B-rays such as Ni, Pm and H as the radioactive material 31.

FIG. 8 shows a fragmentary sectional view of a further embodiment of the multi-digit display apparatus according to the invention. In the Figure, like parts to these in FIG. 1 are designated by like reference symbols. This embodiment is different from the preceding embodiments in that a non-crystalline glass is used as the sealing material 40 for sealing the periphery of the stack of upper plate 1, window plate 2 and electrode board 3. If the sealing material 40 consists of a usual crystalline glass chiefly composed of lead, as the crystalline glass is heated in neutral or reducing atmosphere or air in the sealing operation it would be blackened or assume gray color, or bubbles would be formed in the glass so that it would be rendered into a sponge-like form so that hermetical seal can no longer be obtained. Also, the display electrodes for the afore-mentioned multi-digit display element are usually constituted by metal forming the discharge surface. Therefore, if the crystalline glass is subjected to sealing operation in air, the display electrodes are oxidized since the crystalline glass usually requires a sealing temperature of 400C or above, which leads to irregular glow of the discharge in the display section or increased firing voltage and in extreme cases failure of the glow discharge.

With a non-crystalline glass used as the sealing material 40, the thermal treatment for sealing can be done in neutral or reducing atmosphere or in vacuum, so that the oxidation of the electrodes can be prevented. Thus, it is possible to use a metal of low firing voltage,.for instance tungsten, molybdenum, tantalum and zirconium as the electrode material. Also, while with the crystalline glass it has been necessary to set a low sealing temperature for suppressing the oxidation of the electrodes, with the non-crystalline glass the sealing temperature may be raised to the neiborhood of the softening point of the glass of the upper plate since the problem of the electrode oxidation is overcome. Further, by using a non-crystalline glass as the sealing material as according to the invention it is possible to select the expansion coefficient of the sealing material to be substantially equal to that of the individual plates, so that reliable hermetical seal may be obtained to enhance the reliability of the package.

As has been described in the foregoing, with the multi-digit display apparatus according to the invention, in which the cathodes and anodes are arranged substantially in the same plane and the anodes are provided in portions surrounded by the cathodes and portions surrounding the cathodes, uniform glow may be obtained for the individual parts of the display cathode, so that clear display patterns compared to the prior art may be obtained.

Also, since according to the invention the total area of the anodes is set to be greater than the total area of the cathodes, the firing voltage can be extremely reduced compared to the prior art.

Further, since the window plate defining the individual digits is provided at least on its side facing the display section with color of low light reflection coefficient, the reflection of light by the inner side of the window plate is prevented to obtain very clear glow display patterns.

Furthermore, since according to the invention a radioactive material is provided on the inner wall of the window plate defining the individual digit sections, the delay time in the initiation of the discharge can be extremely reduced compared to the prior art.

Moreover, since according to the invention noncrystalline glass is used as the sealing material, the thermal sealing operation can be done in a neutral or reducing atmosphere or in vacuum, so that it is possible to use a readily oxidizable metal of low firing voltage such as tungsten, molybdenum, tantalum and zirconium as the electrode material. Also, while with the crystalline glass it has been necessary to set a low sealing temperature for suppressing the oxidation of the electrodes, with the non-crystalline glass the problem of the oxidation of electrodes can be overcome, so that it is possible to increase the sealing temperature to the neiborhood of the softening point of the glass of the upper plate. Further, by using a non-crystalline glass as the sealing material as according to the invention it is possible to select the expansion coefficient of the sealing material to be substantially equal to that of the individual plates, so that reliable hermetical seal may be obtained to enhance the reliability of the package.

What is claimed is:

1. A multi-digit display apparatus comprising an electrode board having a plurality of display sections and a transparent plate which is transparent at least for portions facing the individual display sections, said transparent plate and electrode board being stacked, the stack being hermetically sealed around the periphery thereof, said electrode board carrying a plurality of cathode elements arranged in digit-8 groups for the individual display sections and anodes formed in portions surrounded by the individual cathode elements and in portions surrounding the individual cathode elements for each said digit-8 group, said anodes being commonly connected in each said display section and to a terminal for each said display section and corresponding cathode elements in each said display section being electrically connected with each other and to a terminal for each said element, the total area of the anodes in each display section being greater than the total cathode area in that section.

Notice of Adverse Decision in Interference In Interference No. 99,374, involving Patent No. 3,912,964, M. Kouyama,

K. Nakada, T. Odaka, and A. Miyaano-to, MU LTI-DIGIT DISPLAY AP- PARATUS, final judgment adverse to the pa-tentees was rendered May 25, 1977, as to claim 1.

[Ofioial Gazette September 20, 1.977.] 

1. A multi-digit display apparatus comprising an electrode board having a plurality of display sections and a transparent plate which is transparent at least for portions facing the individual display sections, said transparent plate and electrode board being stacked, the stack being hermetically sealed around the periphery thereof, said electrode board carrying a plurality of cathode elements arranged in digit-8 groups for the individual display sections and anodes formed in portions surrounded by the individual cathode elements and in portions surrounding the individual cathode elements for each said digit-8 group, said anodes being commonly connected in each said display section and to a terminal for each said display section and corresponding cathode elements in each said display section being electrically connected with each other and to a terminal for each said element, the total area of the anodes in each display section being greater than the total cathode area in that section. 